The present invention relates to electrically heated water tanks or reservoirs, particularly for domestic use.
Most widely used are the so-called storage heaters having a volume of between 50 and 120 liters. The heaters are provided with a thermostatically regulated electric heating element. The water within the heater is adapted to circulate within the tank by natural thermosyphonic process until substantially the whole volume of the water reaches the required temperature as regulated by the thermostat. The consumption of hot water from a top portion of the heater causes the refilling thereof by cold water entering at the bottom of the tank, which cold water mixes with the warm water contained within the tank. This of course causes a waste of electrical energy, especially where there is not consumed at one time substantially the whole quantity of water contained within the tank.
There exists a second category of electrical water heaters, namely the so-called instant- or flow-heaters, which comprise a small vessel installed at the immediate vicinity of the hot water tap and which are adapted to be actuated by the consumption of water through the tap. Closing the tap automatically deactivates the heating element. These devices require a relatively high power heating element (of about 5 KW) in order to instantly raise the temperature of the water flowing therethrough. Besides the high rated electrical element (which frequently requires a special electrical installation), there is another disadvantage, namely, that there is no possibility to mix the instantly heated water with the cold mains water supply in order to regulate the temperature of the consumed water.
Still another deficiency of the flow heaters resides in that the heating element is usually built-in within the device and therefore not easily replaced in case of its burning up or other failure.
It is the general object of the present invention to overcome the disadvantages of the above-mentioned conventional storage as well as flow domestic water heaters.
It is a further object of the invention to provide a relatively small and therefore more aesthetic and space-saving water heater, which will function both as a storage water heater and as a flow water heater using the existing installation of the conventional large and cumbersome domestic storage heater, and which is readily replaceable for such storage heaters.